Search NASA⌕ Search

SEARCH · Search NASA

Results for “UNIFORM FLOW”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Analysis of Probe Surveys Conducted in the 10-MW TP3 Arc-Jet Facility 15-Inch Nozzle Flow

Computational simulations and analysis of flow characterization tests in a high enthalpy arc-jet facility at NASA Ames Research Center are reported. These tests were conducted in the 10-MW TP3 facility 15-inch conical nozzle, and pitot pressure and heat flux probes are used to survey test flow downstream of the nozzle exit. Two 1.59-cm (0.625 in) diameter hemisphere probes were used: one with a stagnation-point pressure port, the other with a Gardon heat flux gage. Calibration data were also obtained using 10.16-cm iso-q and 20.32-cm flat-faced slug calorimeters. Experimental surveys of arc-jet test flow with pitot pressure and heat flux probes were obtained at eight arc-heater conditions, covering wide ranges in arc current (316–1756 A) and mass flow rate (32–500 g/s, without any cold-gas injection at the arc-heater plenum) and providing assessment of the flow uniformity in the facility. The present analysis comprises computational fluid dynamics simulations of the nonequilibrium flowfield in the facility nozzle and test box, including the models tested. These simulations take into account non-uniform total enthalpy and mass flux profiles at the nozzle inlet as well as the expansion waves emanating from the nozzle exit and their effects on the model flowfields. Comparisons of computations with the experimental measurements are presented, showing reasonably good agreement. The probe survey data and accompanying analysis show that the test flow in the TP3 15-inch nozzle is highly non-uniform at most conditions, and the extent of flow non-uniformity depends on arc current and mass flow rate.

Arc-jets↗
NASA NTRSDate not supplied

Analysis of Probe Surveys Conducted in the 10-MW TP3 Arc-Jet Facility 15-Inch Nozzle Flow

Computational simulations and analysis of flow characterization tests in a high enthalpy arc-jet facility at NASA Ames Research Center are reported. These tests were conducted in the 10-MW TP3 facility 15-inch conical nozzle, and pitot pressure and heat flux probes are used to survey test flow downstream of the nozzle exit. Two 1.59-cm (0.625 in) diameter hemisphere probes were used: one with a stagnation-point pressure port, the other with a Gardon heat flux gage. Calibration data were also obtained using 20.32-cm flat-faced slug calorimeters. Experimental surveys of arc-jet test flow with pitot pressure and heat flux probes were obtained at eight arc-heater conditions, covering wide ranges in arc current (316–1756 A) and mass flow rate (32–500 g/s, without any cold-gas injection at the arc-heater plenum) and providing assessment of the flow uniformity in the facility. The present analysis comprises computational fluid dynamics simulations of the nonequilibrium flowfield in the facility nozzle and test box, including the models tested. These simulations take into account non-uniform total enthalpy and mass flux profiles at the nozzle inlet as well as the expansion waves emanating from the nozzle exit and their effects on the model flowfields. Comparisons of computations with the experimental measurements are presented, showing reasonably good agreement. The probe survey data and accompanying analysis show that the test flow in the TP3 15-inch nozzle is highly non-uniform at most conditions, and the extent of flow non-uniformity depends on arc current and mass flow rate.

Arc-jets↗
NASA NTRS1977

Aerodynamic performance of 0.4066-scale model of JT8D refan stage with S-duct inlet

A scale model of the JT8D refan stage was tested with a scale model of the S-duct inlet design for the refanned Boeing 727 center engine. Detailed survey data of pressures, temperatures, and flow angles were obtained over a range of flows at speeds from 70 to 97 percent of design speed. Two S-duct configurations were tested; one with a bellmouth inlet and the other with a flight lip inlet. The results indicated that the overall performance was essentially unaffected by the distortion generated by the S-duct inlet. The stall weight flow increased by less than 0.5 kg/sec (approximately 1.5% of design flow) with the S-duct inlet compared with that obtained with uniform flow. The detailed measurements indicated that the inlet guide vane (IGV) significantly reduced circumferential variations. For example, the flow angles ahead of the IGV were positive in the right half of the inlet and negative in the left half. Behind the IGV, the flow angles tended to be more uniform circumferentially.

Moore, R. D.↗
NASA NTRS1983

An experimental study of entrainment and transport in the turbulent near wake of a circular cylinder

Attention is given to an experimental investigation of transport processes in the near wake of a circular cylinder, for a Reynolds number of 140,000, in which an X-array of hot wire probes mounted on a pair of whirling arms was used for flow measurement. Rotation of the arms in a uniform flow applies a wide range of relative flow angles to these X-arrays, making them inherently self-calibrating in pitch. A phase signal synchronized with the vortex-shedding process allowed a sorting of the velocity data into 16 populations, each having essentially constant phase. An ensemble average for each population yielded a sequence of pictures of the instantaneous mean flow field in which the vortices are frozen, as they would be on a photograph. The measurements also yield nonsteady mean data for velocity, intermittency, vorticity, stress, and turbulent energy production, as a function of phase. Emphasis is given in a discussion of study results to the nonsteady mean flow, which emerges as a pattern of centers and saddles in a frame of reference that moves with the eddies. The kinematics of the vortex formation process are described in terms of the formation and evolution of saddle points between vortices in the first few diameters of the near wake.

Cantwell, B.↗
NASA NTRS1990

A highly durable injector faceplate design concept for O2/H2 propellants

Two different O2/H2 injector faceplate designs were used in a test bed rocket engine at the NASA Lewis Research Center facility. This test bed was operated in a pulsing mode to evaluate thrust chamber wall materials and coatings. Degradation of the sintered mesh injector face plates resulted in the substitution of a photoetched diffusion-bonded platelet faceplate. This faceplate accumulated over 4200 thermal cycles without damage or degradation. Prior testing for a total of 17,446 cycles required 19 sintered mesh faceplates. This average of 918 cycles per unit showed the diffusion bonded faceplate to have a thermal cycle capability ranging from 150 to 500 percent of that of the sintered wire unit. The test data also showed that the diffusion-bonded faceplate provided a more uniform flow of gaseous H2 through its discrete and uniformly spaced propellant orifices resulting in enhanced face cooling (no local hot spots) and increased performance. The injector faceplate designs are described and the results of the injector comparison test data are presented.

Mueggenburg, H. H.↗
NASA NTRS2002

Lattice Boltzmann Method for 3-D Flows with Curved Boundary

In this work, we investigate two issues that are important to computational efficiency and reliability in fluid dynamics applications of the lattice, Boltzmann equation (LBE): (1) Computational stability and accuracy of different lattice Boltzmann models and (2) the treatment of the boundary conditions on curved solid boundaries and their 3-D implementations. Three athermal 3-D LBE models (D3QI5, D3Ql9, and D3Q27) are studied and compared in terms of efficiency, accuracy, and robustness. The boundary treatment recently developed by Filippova and Hanel and Met et al. in 2-D is extended to and implemented for 3-D. The convergence, stability, and computational efficiency of the 3-D LBE models with the boundary treatment for curved boundaries were tested in simulations of four 3-D flows: (1) Fully developed flows in a square duct, (2) flow in a 3-D lid-driven cavity, (3) fully developed flows in a circular pipe, and (4) a uniform flow over a sphere. We found that while the fifteen-velocity 3-D (D3Ql5) model is more prone to numerical instability and the D3Q27 is more computationally intensive, the 63Q19 model provides a balance between computational reliability and efficiency. Through numerical simulations, we demonstrated that the boundary treatment for 3-D arbitrary curved geometry has second-order accuracy and possesses satisfactory stability characteristics.

Mei, Renwei↗
NASA NTRS2013

Micromachined Active Magnetic Regenerator for Low-Temperature Magnetic Coolers

A design of an Active Magnetic Regenerative Refrigeration (AMRR) system has been developed for space applications. It uses an innovative 3He cryogenic circulator to provide continuous remote/distributed cooling at temperatures in the range of 2 K with a heat sink at about 15 K. A critical component technology for this cooling system is a highly efficient active magnetic regenerator, which is a regenerative heat exchanger with its matrix material made of magnetic refrigerant gadolinium gallium garnet (GGG). Creare Inc. is developing a microchannel GGG regenerator with an anisotropic structured bed for high system thermal efficiency. The regenerator core consists of a stack of thin, single-crystal GGG disks alternating with thin polymer insulating layers. The insulating layers help minimize the axial conduction heat leak, since GGG has a very high thermal conductivity in the regenerator s operating temperature range. The GGG disks contain micro channels with width near 100 micrometers, which enhance the heat transfer between the circulating flow and the refrigerant bed. The unique flow configuration of the GGG plates ensures a uniform flow distribution across the plates. The main fabrication challenges for the regenerator are the machining of high-aspect-ratio microchannels in fragile, single-crystal GGG disks and fabrication and assembly of the GGG insulation layers. Feasibility demonstrations to date include use of an ultrashort- pulse laser to machine microchannels without producing unacceptable microcracking or deposition of recast material, as shown in the figure, and attachment of a thin insulation layer to a GGG disk without obstructing the flow paths. At the time of this reporting, efforts were focused on improving the laser machining process to increase machining speed and further reduce microcracking.

Chen, Weibo↗
NASA NTRS2021

Full Aerothermal Characterization of the NASA Glenn Research Center 9- by 15-Foot Low-Speed Wind Tunnel (2019 Test)

Following completion of the 9- by 15-Foot Low Speed Wind Tunnel acoustic improvement modification project, a characterization of the flow field throughout the 9- by 15-foot test section was conducted in 2019. The acoustic improvement modifications project included several large-scale tunnel loop modifications and reconstruction of the 9- by 15-Foot Low Speed Wind Tunnel test section and diffuser to decrease the noise floor in the test section. Data were collected at three cross-sectional planes in the 9- by 15-ft test section using a 15-foot traversing calibration rake and a set of eight boundary layer rakes. The data from the characterization test were used to generate calibration relationships for facility operation and understand the flow quality in the new test section, including uniformity, flow angularity, turbulence intensity, and boundary layer characteristics. Additionally, the subsonic quick check rake was used to baseline the check calibration data set for the new test section.

Wind↗
NASA NTRSDate not supplied

Test Section Characterization of the 9- by 15-Foot Low Speed Wind Tunnel

Following completion of the 9- by 15-Foot Low Speed Wind Tunnel acoustic improvement modification project, a characterization of the flow field throughout the 9- by 15-foot test section was conducted in 2019. The acoustic improvement modifications project included several large-scale tunnel loop modifications and reconstruction of the 9- by 15-Foot Low Speed Wind Tunnel test section and diffuser to decrease the noise floor in the test section. Data were collected at three cross-sectional planes in the 9- by 15-ft test section using a 15-foot traversing calibration rake and a set of eight boundary layer rakes. The data from the characterization test were used to generate calibration relationships for facility operation and understand the flow quality in the new test section, including uniformity, flow angularity, turbulence intensity, and boundary layer characteristics. Additionally, the subsonic quick check rake was used to baseline the check calibration data set for the new test section.

Calibration↗
NASA NTRS1984

Empirically derived second order schemes for the advection equations with minimum dissipation and dispersion errors

Two second-order advection schemes of the Lax-Wendroff type are empirically derived which have accuracy and phase characteristics similar to that of a third-order scheme. The new schemes are compared with other currently used methods, and are shown to have superior behavior in simulating the advection of localized disturbances. The schemes are derived for constant flow and generalized to two-dimensional non-uniform flow.

Takacs, L. L.↗
NASA NTRS1986

Experimental aerodynamic evaluation of the SSME two-duct, hot gas manifold

An investigation was performed on an improved Space Shuttle Main Engine (SSME) hot gas manifold (HGM) design using a full scale HGM model in cold-flow, air-blowdown tests. The new HGM design replaces the current three transfer ducts with two enlarged elliptical transfer ducts, faired duct inlets, and enlarged fuel bowl. Extensive experimental results have been obtained to verify previous results showing that the two-duct design improved the HGM internal flow path by eliminating separated flow regions, reducing high local velocities, and providing more uniform flow.

Kim, B. Y.↗
NASA NTRS1975

Analysis of liquid-metal-jet impingement cooling in a corner region and for a row of jets

A conformal mapping method was used to analyze liquid-metal-jet impingement heat transfer. The jet flow region and energy equation are transformed to correspond to uniform flow in a parallel plate channel with nonuniform heat addition along a portion of one wall. The exact solution for the wall-temperature distribution was obtained in the transformed channel, and the results are mapped back into the physical plane. Two geometries are analyzed. One is for a single slot jet directed either into an interior corner formed by two flat plates, or over the external sides of the corner; the flat plates are uniformly heated, and the corner can have various included angles. The heat-transfer coefficient at the stagnation point at the apex of the plates is obtained as a function of the corner angle, and temperature distributions are calculated along the heated walls. The second geometry is an infinite row of uniformly spaced parallel slot jets impinging normally against a uniformly heated plate. The heat-transfer behavior is obtained as a function of the spacing between the jets. Results are given for several jet Peclet numbers from 5 to 50.

Siegel, R.↗
NASA NTRS1985

Calculation of flow about posts and powerhead model

A three dimensional analysis of the non-uniform flow around the liquid oxygen (LOX) posts in the Space Shuttle Main Engine (SSME) powerhead was performed to determine possible factors contributing to the failure of the posts. Also performed was three dimensional numerical fluid flow analysis of the high pressure fuel turbopump (HPFTP) exhaust system, consisting of the turnaround duct (TAD), two-duct hot gas manifold (HGM), and the Version B transfer ducts. The analysis was conducted in the following manner: (1) modeling the flow around a single and small clusters (2 to 10) of posts; (2) modeling the velocity field in the cross plane; and (3) modeling the entire flow region with a three dimensional network type model. Shear stress functions which will permit viscous analysis without requiring excessive numbers of computational grid points were developed. These wall functions, laminar and turbulent, have been compared to standard Blasius solutions and are directly applicable to the cylinder in cross flow class of problems to which the LOX post problem belongs.

Anderson, P. G.↗
NASA NTRS1985

Effects of upstream-biased third-order space correction terms on multidimensional Crowley advection schemes

The impact of upstream-biased corrections for third-order spatial truncation error on the stability and phase error of the two-dimensional Crowley combined advective scheme with the cross-space term included is analyzed, putting primary emphasis on phase error reduction. The various versions of the Crowley scheme are formally defined, and their stability and phase error characteristics are intercompared using a linear Fourier component analysis patterned after Fromm (1968, 1969). The performances of the schemes under prototype simulation conditions are tested using time-dependent numerical experiments which advect an initially cone-shaped passive scalar distribution in each of three steady nondivergent flows. One such flow is solid rotation, while the other two are diagonal uniform flow and a strongly deformational vortex.

Schlesinger, R. E.↗
NASA NTRS2015

Development of Test Protocols for International Space Station Particulate Filters

Air quality control on the International Space Station (ISS) is a vital requirement for maintaining a clean environment for the crew and the hardware. This becomes a serious challenge in pressurized space compartments since no outside air ventilation is possible, and a larger particulate load is imposed on the filtration system due to lack of gravitational settling. The ISS Environmental Control and Life Support System (ECLSS) uses a filtration system that has been in use for over 14 years and has proven to meet this challenge. The heart of this system is a traditional High-Efficiency Particulate Air (HEPA) filter configured to interface with the rest of the life support elements and provide effective cabin filtration. The filter element for this system has a non-standard cross-section with a length-to-width ratio (LW) of 6.6. A filter test setup was designed and built to meet industry testing standards. A CFD analysis was performed to initially determine the optimal duct geometry and flow configuration. Both a screen and flow straighter were added to the test duct design to improve flow uniformity and face velocity profiles were subsequently measured to confirm. Flow quality and aerosol mixing assessments show that the duct flow is satisfactory for the intended leak testing. Preliminary leak testing was performed on two different ISS filters, one with known perforations and one with limited use, and results confirmed that the testing methods and photometer instrument are sensitive enough to detect and locate compromised sections of an ISS BFE.Given the engineering constraints in designing spacecraft life support systems, it is anticipated that non-industry standard filters will be required in future designs. This work is focused on developing test protocols for testing the ISS BFE filters, but the methodology is general enough to be extended to other present and future spacecraft filters. These techniques for characterizing the test duct and perform leak testing can be applied to conducting acceptance testing and inventory testing for future manned exploration programs with air revitalization filtration needs, possibly even for in-situ filter element integrity testing for extensively long-duration missions. We plan to address the unique needs for test protocols for crewed spacecraft particulate filters by preparing the initial version of a standard, to be documented as a NASA Technical Memorandum (TM).

Filtration↗
NASA NTRS1979

Procedure for noise prediction and optimization of advanced technology propellers

The sound field due to a propeller operating at supersonic tip speed in a uniform flow was investigated. Using the fact that the wave front in a uniform stream is a convected sphere, the fundamental solution to the convected wave equation was easily obtained. The Fourier coefficients of the pressure signature were obtained by a far field approximation, and are expressed as an integral over the blade platform. It is shown that cones of silence exist fore and aft the propeller plane. The semiapex angles are shown. These angles are independent of the individual Mach components such as the flight Mach number and the rotation Mach number. The result is confirmed by the computation of the ray path of the emitted Mach waves. The Doppler amplification factor strengthens the signal behind the propeller while it weakens that upstream.

Jou, W. H.↗
NASA NTRS1992

Flow characterization in the NASA Ames 16-inch Shock Tunnel

Flow characteristics of NASA's 16-Inch Shock Tunnel are determined for purposes of providing hypersonic propulsion simulation capability. The key tunnel operating parameters are the incident shock speed and reservoir pressure and enthalpy. Flow characteristics of concern are the nozzle exit pressure, temperature, Mach number, Reynolds number, chemical composition, and flow uniformity. Surface mounted gages (for pressure and heat transfer) and nonintrusive optical flow diagnostics (emission and absorption spectroscopy and holographic interferometry) are used to verify tunnel conditions. Experimental measurements are used to validate computational analysis for predicting facility performance, and CFD is used to interpret the free stream optical diagnostic measurements.

Cavolowsky, John A.↗